Bracts in Welwitschia mirabilis . 
55i 
are comparatively few in the lower part of the bract, and are scattered here 
and there along the bundle. Higher up in position they increase in amount, 
and are better developed on the phloem side. In these cases the tracheides 
are generally elongated in the longitudinal direction. Towards the apex of 
the bract, where the bundles ramify freely, the tracheides reach their maxi- 
mum development. They surround the bundles nearly completely. They 
often even extend in lateral directions, and sometimes they occupy the 
space between bundles, thus replacing a large part of the mesophyll. The 
elements are not always connected with each other, but occasionally occur 
isolated among the mesophyll-parenchyma. The general disposition of the 
tracheides can be very well seen in a preparation cleared with eau de 
Javelle (Text-fig. 2). 
The first-formed elements arise usually on the lateral side of the bundle, 
just as in the case of the leaf and cotyledon . 1 The later-formed elements 
are derived from mesophyll-parenchyma, which can be traced by comparison 
with adjacent cells. 
The same structure occurs in the bracts of Gnetum and of Ephedra 
(not in the male inflorescence), as well as in the female cone-scales of the 
Conifers, which have been fully investigated by Bernard . 2 
Summary and Conclusions. 
It has been pointed out above that there occur two kinds of bracts in 
the inflorescence, viz. those at the node of the inflorescence axis, and those 
in the cone. There is no morphological and anatomical difference between 
them, and they are perfectly homologous. All the bracts are broadly ovate 
and are, except those in the upper portion of the female cone, connate 
at the base. 
Each bract receives a pair of bundles which branch copiously towards 
the apex of the bract. The nervation is closely comparable with that of 
the cotyledon, which possesses the phylogenetically primary arrangement of 
vascular supply. 
In the outer epidermis stomata are found abundantly, and in their 
structure they are identical with those of the leaf. Chloroplasts are present 
in the epidermal cells of the cone-scale. 
The mesophyll is differentiated into palisade tissue and roundish 
parenchyma cells. These are full of chloroplasts and form chlorenchyma. 
Spicular cells with crystals of calcium oxalate and sclerenchymatous fibres 
with unlignified walls are present in the mesophyll. Irregularly branched 
mucilage canals are also found in abundance. 
1 Cf. Takeda, H., 1 . c., p. 354. 
2 Bernard, Ch. : Le bois centripete dans les bractees et dans les ecailles des Coniferes, in 
Beihefte z. Bot. Centralbl., xvii, 1904. 
